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TMCNet:  DOE Creates Its Own Solar X-Prize [Mechanical Engineering]

[November 10, 2012]

DOE Creates Its Own Solar X-Prize [Mechanical Engineering]

(Mechanical Engineering Via Acquire Media NewsEdge) The he U.S. Department of Energy has announced a $10 million prize to the first three companies that can slash the non-hardware costs of plugging in home and business rooftop solar power systems to $1 per watt, from about $1.55 now. The prize is part of DOE's SunShot Initiative, which seeks to make unsubsidized solar energy competitive with gas, oil, nuclear, and hydroelectric energy by the end of the decade.


The rapid decline in the cost of solar hardware- 75 percent in just four years- has sparked broad optimism in the field. A recent study by McKinsey & Co. projected that total solar capacity could reach 400 to 600 gigawatts in 2020, up from 65 GW in 2011. By 2020, the industry could be adding 75 to 100 GW of new capacity annually, even without subsidies.

Yet the total cost of linking that hardware into the grid remains obstinately high. These "soft" costs include permitting, licensing, system engineering, and connecting to the grid. According to DOE, soft costs account for roughly half the installed cost of residential and commercial solar systems.

The SunShot Prize seeks to slash this by 65 percent to $1 a watt by 2015. DOE hopes ultimately to push soft costs down to 60 cents per watt by 2020. This is critical to slicing total installed costs for residential solar to $1.50 a watt from $5.71 in 2010 and commercial to $1.25 a watt from $4.59 over the same period.

The SunShot Prize sounds like an X-Prize. Both have ambitious targets and large awards, and both rely on entrepreneurial partnerships to fill in the details. The SunShot Prize winner will receive $7 million, and second- and third-place runners up will get $2 million and $1 million, respectively.

The difference is that X-Prizes go to prototypes and SunShot Prizes require commercial installations. The Phase I winners must deploy 5,000 small-scale rooftop systems of 2 to 15 kilowatts each. For Phase II, winners must install another 1,000 systems so DOE can judge their business sustainability.

Soft costs are DOE's latest target. DOE's SunShot Incubator program focused on hardware. Since 2007, it provided $60 million for hardware startups (including ill-fated Solyndra), which helped them raise more than $1.3 billion in private investment.

Solar has been attracting lots of attention from startups, large businesses, and universities. Here is a sampling: ROBOTIC TRACKING QBotix of Menlo Park, Calif., has developed a robot that can keep hundreds of solar panels facing the sun during the day. By switching to robotic adjustment and eliminating the controls, motors, and complex mounting systems now used in solar tracking systems, QBotix claims grid-sized solar parks can reduce their project break-even cost by 20 percent.

A typical grid-sized solar park, in order to achieve high power output, must keep its solar panels facing the sun. Some systems do this by turning their panels along a single axis (east to west). This increases power output by about 25 percent. Engineers can lift that to 40 percent by adding a second axis that also tracks the sun's height up and down.

Tracking systems make solar parks expensive and complex, since each panel requires its own controller, motors, mounting system, and concrete foundation. Multiply that by hundreds of panels, and it is easy to see why solar balance of system and maintenance costs can be a problem.

The QBotix tracking system moves the controllers and motors from the panels into a single robot. The robot scoots along a monorail track, adjusting each panel it passes every 40 minutes. A single robot can keep hundreds of panels (up to 300 kilowatts' worth) facing the sun. A backup robot provides system redundancy.

Solar park operators eliminate the capital and maintenance cost of hundreds of motors and controllers. They can also simplify panel mounting systems while optimizing cost, strength, durability, and ease of installation.

QBotix claims robots provide dual axis tracking for the cost of a single axis system.

QBotix has run a prototype for the past year and raised $7.5 million in venture capital. One of the investors is Siemens Venture Capital. Siemens Technology-ToBusiness, a Siemens unit that helps market new technologies, recently finished a yearlong qualification of the QBotix system for deployment.

OPTIMIZING RENEWABLES In addition to investing in QBotix and other new technologies, Siemens, like many other large power companies, also produces systems designed specifically for renewable (not just solar) energy.

Its latest offerings, the turnkey Motion-to-Grid, or M2G, energy converter, turns variable electromechanical energy produced by wind, wave, tidal, geothermal, and biomass turbine generators into reliable, harmonic-free, three-phase energy for a utility grid.

Siemens recommends M2G for small-scale power systems. Users can connect any type of three-phase generator (induction or permanent magnet) to the converter, select the amplitude, and produce clean, sinusoidal, three-phase voltage that meets IEEE 1547 harmonic standards and synchronizes with any weak or strong grid.

The system consists of a configurable ac input/ac output inverter and turbine (and generator) controller enclosed in two indoor or outdoor rated cabinets. One houses one or more turbine converters with a centralized control and operations interface. The second, which interfaces with the grid, comes with a 30 to 200 kW range of power levels, and optional output to 4 megawatts.

The system consists of off-the-shelf Drive-Cliq drive components that users can replace without re-commissioning. Also standard are advanced generator control algorithms that let users switch between servo or vector modes and generating or motoring modes.

M2G also supports real-time control loop adjustment and ongoing drive variable monitoring. A second set of algorithms controls energy generation and provides advanced power protection functionalities.

Siemens will package the system in flexible configurations. It will release the first two, 100 and 55 kilowatts, during the fourth quarter of 2012.

IMPROVING SOLAR ECONOMICS Another way to improve returns is to take advantage of fluctuations in the price of electricity, which can vary as much as 50 percent every day. Solar systems can do this by storing electricity and releasing it during peak demand, when public utilities pay more for power.

A paper by Reza Arghandeh and his doctoral advisor, Robert Broadwater of Virginia Tech's Department of Electrical and Computer Engineering, showed how to make that strategy work with residential and small commercial systems. The 2012 ASME Power Conference and International Conference on Nuclear Engineering named it best student paper.

The system Arghandeh and Broadwater envision consists of an array of batteries connected to distribution transformers. The batteries would store electricity generated by distributed photovoltaic systems. The system would then bid the power to market when rates rose.

The key to their approach is to optimize the economics of bidding. It is based on such elements as realtime rate fluctuations, daily weather forecasts, projected electrical load variations, and the amount of electrical reserves needed for backup power in case of power loss. The algorithm's output is a distributed energy storage charging and discharging schedule that maximizes operational benefits.

Electrical Distribution Design of Blacksburg, Va., a firm that makes utility industry software, funded the research.

Siemens" Motion-to-Grid energy converters are designed for small systems.

(c) 2012 American Society of Mechanical Engineers

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